Indian Journal of Sexually Transmitted Diseases and AIDS
: 2007  |  Volume : 28  |  Issue : 2  |  Page : 108--109

Clue cells

Kaleem J Khan, Rajul Shah, Manjyot Gautam, Sharmila Patil 
 Department of Dermatology, Venereology and Leprosy, Pad. Dr. D.Y. Patil Hospital, Nerul, Navi Mumbai, India

Correspondence Address:
Kaleem J Khan
Al-Sana House, Behind Vidyanidhi School, JVPD Scheme, Mumbai - 400 049

How to cite this article:
Khan KJ, Shah R, Gautam M, Patil S. Clue cells.Indian J Sex Transm Dis 2007;28:108-109

How to cite this URL:
Khan KJ, Shah R, Gautam M, Patil S. Clue cells. Indian J Sex Transm Dis [serial online] 2007 [cited 2023 Dec 10 ];28:108-109
Available from:

Full Text

Clue cells were first described by Gardner and Dukes [1] in 1955 and were so named as these cells give an important "clue" to the diagnosis of bacterial vaginosis (BV).

Clue cells are vaginal squamous epithelial cells coated with anaerobic Gram-variable coccobacilli Gardnerella vaginalis . [2]


An increase in vaginal pH occurs due to alteration in normal flora characterized by a decrease in lactobacilli [3] ( Doderlein bacilli ) and increase in bacteria such as G. vaginalis , Mycoplasma hominis and anaerobes such as Mobiluncus , Bacteroides and Peptostreptococcus species.

Factors that cause these changes in flora are poorly understood; however, the postulates [4],[5] include the menstrual cycle, concomitant infections, sexual activity, contraceptive methods and antibiotic use.

Thus, an increase in local pH is favorable to the growth of bacteria causing BV. These bacteria adhere to the surface of epithelial cells leading to the formation of clue cells.

 Demonstration of Clue Cells

Clue cells can be demonstrated by microscopic examination of vaginal wet mount preparation.

From the speculum, an appropriate amount of vaginal discharge is transferred on the glass slide and a droplet of normal saline is added directly. The preparation is covered with a coverslip and examined under a light microscope at 100� (low power) and 400� (high power) magnifications.

The normal vaginal squamous epithelial cells have distinct cell margins and lack granularity. Clue cells are seen as squamous epithelial cells with a large number of coccobacillary organisms densely attached in clusters to their surfaces, giving them a granular appearance. The edges of squamous epithelial cells, which normally have a sharply defined cell border, become indistinct or stippled [Figure 1]. Polymorphonuclear leukocytes (PMNs) can also be demonstrated on the normal vaginal wet mount preparation [Figure 2]. The vaginal discharge of patients with BV is notable for its lack of PMNs, typically 1 or less than 1 PMN per vaginal epithelial cell.

 Clinical Significance

The detection of clue cells is the most useful single procedure for the diagnosis of BV. Presence of more than 20% clue cells in vaginal discharge is included in Amsel's [6] criteria for the diagnosis of BV. Other criteria for the diagnosis of BV include:

milky, homogeneous, adherent discharge;vaginal pH greater than 4.5;positive Whiff test, i.e. typical fishy odor on addition of one or two drops of 10% KOH to vaginal discharge andfew or no lactobacilli.

The presence of any three of the above five conditions is considered diagnostic.

The sensitivity and specificity of more than 20% clue cells on wet mount [7] for diagnosis of BV is 81% and 99%.

The identification of clue cells can also be done on Papanicolaou smear sampled from the posterior fornix with sensitivity [8] and specificity of 90% and 97%, respectively.


1Gardner HL, Dukes CD. Haemophilus vaginalis vaginitis: A newly defined specific infection previously classified "Nonspecific" vaginitis. Am J Obstet Gynecol 1955;69:962-76.
2Scott TG, Smyth CJ, Keane CT. In vitro adhesiveness and biotype of Gardnerella vaginalis strains in relation to the occurrence of clue cells in vaginal discharges. Genitourin Med 1987;63:47-53.
3Eschenbach DA, Davick PR, Williams BL, Klebanoff SJ, Young-Smith K, Critchlow CM, et al . Prevalence of hydrogen peroxide-producing Lactobacillus species in normal women and women with bacterial vaginosis. J Clin Microbiol 1989;27:251-6.
4Saidi SA, Mandal D, Curless E. Bacterial vaginosis in a district genitourinary medicine department: Significance of vaginal microbiology and anaerobes. Int J STD AIDS 1994:5:405-8.
5Sobel JD. Vaginitis. N Engl J Med 1997;337:1896-903.
6Amsel R, Totten PA, Spiegel CA, Chen KC, Eschenbach D, Holmes KK. Nonspecific vaginitis. Diagnostic criteria and microbial and epidemiologic associations. Am J Med 1983;74:14-22.
7Chandeying V, Skov S, Kemapunmanus M, Law M, Geater A, Rowe P. Evaluation of two clinical protocols for the management of women with vaginal discharge in southern Thailand. Sex Transm Infect 1998;74:194-201.
8Platz-Christensen JJ, Larsson PG, Sundstrom E, Bondeson L. Detection of bacterial vaginosis in Papanicolaou smears. Am J Obstet Gynecol 1989;160:132-3.